Question: Let $f(x) = -8x^{2}+9x+7$. Where does this function intersect the x-axis (i.e. what are the roots or zeroes of $f(x)$ )?
Explanation: The function intersects the x-axis when $f(x) = 0$ , so you need to solve the equation: $-8x^{2}+9x+7 = 0$ Use the quadratic formula to solve $ax^2 + bx + c = 0$ $x = \dfrac{-b \pm \sqrt{b^2 - 4ac}}{2a}$ $a = -8, b = 9, c = 7$ $ x = \dfrac{-9 \pm \sqrt{9^{2} - 4 \cdot -8 \cdot 7}}{2 \cdot -8}$ $ x = \dfrac{-9 \pm \sqrt{305}}{-16}$ $ x = \dfrac{-9 \pm \sqrt{305}}{-16}$ $x =\dfrac{-9 \pm \sqrt{305}}{-16}$